1. Field of the Invention
This disclosure relates to the field of cardiovascular exercise machines. In particular, to treadmills which utilize a lifting mechanism with multiple fixed mounting points on the treadbase to permit for high-incline, e.g. greater than 15% incline, of the treadbase.
2. Description of the Related Art
The benefits of regular aerobic exercise on individuals of any age are well documented in fitness science. Aerobic exercise can dramatically improve cardiac stamina and function, as well as lead to weight loss, increased metabolism, and other benefits. At the same time, aerobic exercise has often been linked to damaging effects, particularly to joints or similar structures, where the impact from many aerobic exercise activities can cause injury. Therefore, those involved in the exercise industry are continuously seeking ways to provide users with exercises that have all the benefits of aerobic exercise, without the damaging side effects.
One relatively low impact exercise is walking. Walking has a number of advantages over its faster relative, running. In particular, walking causes much less stress on body structures in the legs, feet, and hips. In a walking motion, the human body generally never completely leaves the ground while in a running motion, the body is suspending midair for a short period of time with each stride. Thus, while walking, knees and other structures absorb an impact from the foot's contact with a surface, but the entire weight of the individual is generally not absorbed by the body as it is in running. For this reason, walking is generally an acceptable exercise for a large number of people even for the elderly and those with joint or other issues. Further, the impact of walking can be further reduced by walking on a treadmill or other exercise device as opposed to walking outside. The treadbase of a treadmill can be purposefully engineered to absorb and reduce impact from footfalls, making the walking motion produce even less impact on the body.
Walking as an exercise, however, has a number of built-in limitations and these can be exaggerated when one is intending to walk on a machine in the home or gym such as a treadmill. Many of the problems relate to walking's built in limitations for strenuousness. The average human will generally naturally walk around 3 to 3.5 miles per hour and most humans cannot walk above 4 to 5 miles per hour without specific training. Generally, at higher speeds, the person has to switch to a running motion in order to maintain the desired speed. It is often accepted that speeds between 4 and 6 miles per hour require the average human to jog, while speeds above 6 miles per hour require a running motion. Humans can obtain very fast speeds while running with an average person being able to sprint at over 10 miles per hour. Further, some studies have indicated that any person's natural walking speed may be preferentially selected to minimize work for desired distance and time. Thus, natural walking as an exercise can be problematic because humans may naturally walk in a very efficient fashion, which can minimize its exercise potential.
While a sustained speed of 4 mph can prove plenty strenuous for many people, for those looking for weight loss and strong cardiovascular workouts, walking, even at their top sustainable speed, can require a very long workout to be equivalent to a relatively short run and the time for such a workout may not be available. The time required by walking can be particularly problematic for home exercise machines where the average user can find walking in-place for a long period of time boring since there is no changing scenery or people to talk to.
For those who are interested in using an exercise machine for strenuous walking, the common way to increase the strenuousness of the activity is to increase the incline of the treadbase forcing them to consistently walk “uphill” or engage in more of a hiking or climbing exercise. Walking at even a relatively slight angle above neutral (or level) has been shown to dramatically increase the strenuousness of the walking. However, traditional treadmills often have problems producing higher inclines. Specifically, traditional treadmills could generally only obtain a maximum incline of around 10-15 percent. In many cases, this was due to the method of lifting and inclining the treadbase.
Traditionally, in order to provide for robust mechanical lifting and a solid treadbase support, treadbases lifted by raising the front end directly upward or upward and forward using a lift mechanism located under the front end of the treadbase. This results in the backend of the treadbase “sliding” across the floor because the treadbase generally cannot alter in length during the raising. This type of raising provides the treadmill with a good stable structure and mechanically simple lift, but it is inherently limited because the lift mechanism (which is generally some form of extending or rotating arm) can generally extend to a maximum of double its totally retracted length and the retracted length needs to fit under the treadbase at its neutral position. Thus, incline was often limited by a desire to keep the treadbase close to the floor in its neutral position. To get high-incline, prior devices often used a fixed high incline (with a neutral position above 15% incline) to avoid having to lift and lower the treadbase and then provided a “stair belt” which simulated climbing stairs as opposed to walking up an incline.
Recently, a new class of high-incline treadmills, which are often marketed as climbing or hiking simulators, have gained in popularity. These devices provide a treadbase without stair structures, and allow for the treadbase to be tilted above the 15% position. For the purposes of this disclosure, a high-incline treadmill is a treadmill which is capable of having the treadbase, and an associated flat (as opposed to stair) endless belt being run thereon, tilt to an angle of greater than 15% from neutral, greater than 20% of neutral, or greater than 30% of neutral and which can depress the treadbase to the neutral position of 0% (or lower) as well. To put it another way, a high-incline treadmill will generally have a variable range of incline greater than 15%, greater than 20%, or greater than 30%. Generally, the treadbase will have a maximum incline of around 30 to 45%, but this is by no means required and higher inclines can be used. However, above 45%, a user maintaining sufficient friction with a flat belt to not slip can be difficult.
Previously, high-incline treadmills shared a couple of commonalities in lift systems which all have specific problems. Prior designs of high-incline treadmills generally utilize a single fulcrum arm to raise and lower the treadbase. Like in traditional treadmills, for mechanical simplicity this is usually an extendable arm (e.g. utilizing a screw or worm drive, hydraulics, or pneumatics) mounted with one end rotatably affixed to the floor stand and one end rotatably affixed to the lower surface of the treadbase. This system is simple as it allows for the drive mechanism to extend or retract (changing its length) and the length change resulted in the treadbase being tilted upward because the only other adjustable variable is the relative angles of the various components. Basically, the systems created a triangular arrangement with two fixed side lengths and one variable (the length of the extension arm) and the ability to alter internal angles.
These types of systems, however, generally require that the extendable arm be mounted toward the rear of the treadbase and the front of the floor stand to obtain enough angle adjustment to get high-incline. With this type of arrangement, the fixed portion of the triangular distance related to the treadbase is shortened (because not all the length of the treadbase is used). Thus, the back of the treadbase is effectively a lever to increase the distance the front end is raised. However, the arrangement generally means that the treadbase is tilted from a position toward the rear of the treadbase. While this provides for a dramatic increase in angle for a relatively small extension, it also means that the front of the treadbase is generally not as strongly supported and can therefore bounce significantly more than may be desirable when a user walks or runs on the treadmill.
Some alternative lifting devices have been proposed, but, for the most part, they rely on the same principle of getting the higher angle by pushing toward the rear of the base. These designs can attach an arm toward the rear of the treadbase in rotational fashion and then rotate the arm with the extension drive to a greater angle (while keeping the length constant). Those few devices which have attempted to connect a support toward the forward end, generally have the support moveably attached to the forward end of the treadbase on rollers or in another similar fashion. Thus, as the incline increases, the connection point to the treadbase will move further back, again suspending the end of the treadbase at higher inclines leading to increased bounce and flexibility of the treadbase at higher inclines, particularly toward the forward end.